Dynamoelectric machines, including brushless D.C. motors and conventional D.C. permanent magnet motors, have been known for many years. A typical dynamoelectric machine has phased windings in a stator and permanent magnets on a rotor. The two components are separated by an air gap so that rotation of the rotor may occur.
Brushless and conventional permanent magnet D.C. motors are described, for example, in the engineering handbook entitled "D.C. Motors, Speed Controls, Servo Systems" (5th Ed., 1980) published by Electro-Craft Corporation, Hopkins, Minn., U.S.A. and reference may be made thereto to ascertain the current state of the art.
Some features of the prior art are employed in specific applications of the concepts of the invention. From the prior art, it is known to provide disc motors with axial air gaps, disc motors with permanent magnet poles on the rotor and phased windings on the stator, disc motors with ferrite permanent magnet poles on the rotor, disc motors with more than one rotor disc on a common shaft and with more than one wound stator interposed among the rotor discs to obtain multiple torque-producing combinations, motors with an even number of poles on the rotor, motors with the same number of poles on rotor and stator, motors with different numbers of poles on rotor and stator, motors with windings in slots in the stator, motors with windings distributed on the air-gap surface of the stator and no stator slots, and motors of concentric cylindrical shape as an alternative to the disc-like form.